Papers of the Week

Ion channels serve pleiotropic functions. Often found in complexes, their activities and functions are sculpted by auxiliary proteins. We discovered that collapsin response mediator protein 2 (CRMP2) is a binding partner and regulator of the N-type voltage-gated calcium channel (Ca2.2), a genetically validated contributor to chronic pain. Herein, we trace the discovery of a new peptidomimetic modulator of this interaction, starting from the identification and development of CBD3, a CRMP2-derived Ca binding domain peptide. CBD3 uncouples CRMP2-Ca2.2 binding to decrease Ca2.2 surface localization and calcium currents. These changes occur at presynaptic sites of nociceptive neurons and indeed, CBD3 ameliorates chronic pain in preclinical models. In pursuit of a CBD3 peptidomimetic, we exploited a unique approach to identify a dipeptide with low conformational flexibility and high solvent accessibility that anchors binding to Ca2.2. From a pharmacophore screen, we obtained CBD3063, a small-molecule that recapitulated CBD3’s activity, reversing nociceptive behaviors in rodents of both sexes without sensory, affective, or cognitive effects. By disrupting the CRMP2-Ca2.2 interaction, CBD3063 exerts these effects indirectly through modulating Ca2.2 trafficking, supporting CRMP2 as an auxiliary subunit of Ca2.2. The parent peptide CBD3 was also found by us and others to have neuroprotective properties at postsynaptic sites, through -methyl-d-aspartate receptor and plasmalemmal Na/Ca exchanger 3, potentially acting as an auxiliary subunit for these pathways as well. Our new compound is poised to address several open questions regarding CRMP2’s role in regulating the Ca2.2 pathways to treat pain with the potential added benefit of neuroprotection.